Paracoccidioides brasiliensis is a fungus that lives in the environment and causes paracoccidioidomycosis (PCM). This fungus is dimorphic, meaning it exists in two forms depending on its environment. Outside a host, in cooler temperatures, it grows as a mold. Inside the human body, where temperatures are warmer, it transforms into a yeast-like form, which causes disease.
Geographic Distribution and Transmission
Paracoccidioides brasiliensis is primarily found in Latin America. The highest incidence of paracoccidioidomycosis is in Brazil, with significant cases also reported in Venezuela, Colombia, and Argentina. The fungus thrives in humid soil, particularly in areas with constant rainfall and a rich protein content, often associated with agricultural activities such as coffee and tobacco cultivation.
People become infected by inhaling spores from the air, typically when soil is disturbed. While the fungus is present in the environment, only a small percentage of those exposed develop the disease. Paracoccidioidomycosis is not contagious and cannot be transmitted from person to person.
Forms of Paracoccidioidomycosis
Once fungal spores are inhaled, the infection can remain dormant for years without causing symptoms. If symptoms develop, they vary depending on affected body areas. Paracoccidioidomycosis manifests in two main clinical forms: the chronic (adult) form and the acute/subacute (juvenile) form.
The chronic form is most common, typically affecting adults over 30, sometimes decades after initial exposure. This form progresses slowly and often impacts the lungs, leading to symptoms such as a persistent cough, shortness of breath, and increased mucus production. Lung involvement can appear as infiltrates on imaging and may lead to progressive scarring or fibrosis. The disease can also spread beyond the lungs, causing painful lesions or ulcers in the mouth, nose, and on the skin, and may affect other organs like the adrenal glands.
The acute/subacute (juvenile) form is less common and more aggressive. This form usually affects children and young adults, often within weeks or months of exposure. It primarily targets the reticuloendothelial system, which includes organs involved in immune function. Common symptoms include fever, weight loss, and enlarged lymph nodes, liver, and spleen. Skin and mucous membrane lesions can also be present, and in severe instances, bone involvement may occur.
At-Risk Populations
Paracoccidioidomycosis disproportionately affects adult males, particularly those engaged in agricultural work. This demographic is more likely to encounter the fungus in soil during activities like farming or mining. The male-to-female ratio for the chronic form can be as high as 15:1 to 22:1 in some endemic areas of Brazil.
One leading scientific explanation for this gender disparity involves the protective role of female hormones. Estrogen, a female hormone, is believed to inhibit the fungus from transforming into its invasive yeast form inside the body. This hormonal effect may reduce disease progression in women, even with similar exposure rates. Individuals with weakened immune systems, such as those with HIV, are also at increased risk of developing more severe or disseminated forms.
Diagnosis and Treatment
Diagnosis often involves identifying the fungus in patient samples. Doctors typically use direct microscopic examination of tissue or sputum samples to look for the fungus’s characteristic “mariner’s wheel” or “Mickey Mouse” appearance, which refers to the mother cell surrounded by multiple peripheral daughter cells. Fungal cultures can also be grown from these samples to confirm the presence of Paracoccidioides brasiliensis. Blood tests, known as serology, can detect antibodies produced by the body in response to the fungal infection. Imaging techniques, such as chest X-rays, are used to assess lung involvement, especially in the chronic form.
Treatment relies on antifungal medications. Itraconazole is generally the standard treatment for most mild to moderate cases, showing high effectiveness. For more severe infections, or in immunocompromised patients, amphotericin B is often used as an initial therapy. Other antifungals like voriconazole, posaconazole, and trimethoprim-sulfamethoxazole may also be used as alternatives. Treatment is typically long-term, lasting from several months to years, to ensure the infection is fully cleared and to minimize the risk of relapse.